We have a Geriatric Anesthesia Research Unit in the Department of Anesthesia, which makes measurement of preoperative, intraoperative and postoperative status of patients in sixth through ninth decade, focusing on the anesthetic, cardiac and respiratory responses. This is not a service unit. But we do anesthetize patients using all modern adjuvants to anesthesia and monitoring, and capitalize on these opportunities for invasive studies. The stresses of anesthesia, surgery and recovery offer opportunity to evaluate functional status-reserver in ways not attempted in ordinary elderly people. Our primary effort involves study of the ventilatory response to carbon dioxide and its modulation by premedication, anesthesia, and operation. Similarly when central catheters are already placed for the patient's care we study the circulatory response to carbon dioxide. Finally, recognizing the advantages of spinal block, we are trying to partition the importance of the many factors affecting control of the level of anesthesia.